Transcript INTRO. TO GENETICS

GENESIS 1:11,21,24
Then God said, “Let the land produce vegetation: seed-bearing plants and
trees on the land that bear fruit with seed in it, according to their various kinds.
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So God created the great creatures of the sea and every living and moving
thing with which the water teems, according to their kinds, and every winged
bird according to its kind, and God saw that it was good.
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And God said, “Let the land produce living creatures according to their kinds:
livestock, creatures that move along the ground, and wild animals, each
according to its kind, and it was so.
INTRO. TO GENETICS
• Genesis 1:11,21,24
• Heredity- biological inheritance; brings differences between
species
• Genetics- branch of biology that studies heredity
• Early ideas about heredity
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Blended traits
• Gregor Mendel: Monk, 1850’s did work leading to genetics
• Self-pollination: Pollen produced by the plant, fertilizes the egg of
the same plant. Offspring inherit all characteristics from one plant
• Cross-pollination: Pollen produced by the plant, fertilizes the egg
of another plant. Offspring inherit characteristics of both plants.
• Purebred: Offspring having only one form of a trait w/ea. Gen.
• Traits: Characteristics that can be passed on to offspring
GENES AND DOMINANCE
• Hybrids: Organisms produced by crossing parents with differing
characteristics.
• Mendel crossed Tall/short & Yellow/green. Results?????????
• Genes: Factors that control traits; segment of DNA that codes for
a particular protein.
• Alleles: Different forms of a gene for a specific trait. Ex. Tall/short
• Principle of Dominance
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Dominant alleles- are present with contrasting recessive alleles.
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Recessive alleles- are not observed in the presence of
dominant alleles
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Although dominance is seen in many traits, it doesn’t apply to
all genes
SEGREGATION
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What happened to the recessive characteristics?
P generation-parental plants
F-1 generation- first generation of plants produces by crosspollinating them among themselves.
F-2 generation- F-1 plants crossed with themselves
THE F-1 CROSS:
The recessive characters had not disappeared in all plants.
Why did the recessive alleles disappear in the F1 generation
and reappear in the F2?
SEGREGATION: (separation) separation of alleles during gamete
formation.
INDEPENDENT ASSORTMENT
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Does the segregation of one pair of alleles affect the
segregation of another pair of alleles? (Must a round seed by
yellow?)
THE TWO FACTOR CROSS:
RRYY or rryy
Fig. 9-9: remember we’re looking at kind of seeds produced
What is the phenotype of the F1 generation?
We need the seeds from the F2 to test our theory
Fig. 9-10
What happens when we cross F1? Do RY and ry show up?
If genes aren’t connected they segregate independently
Independent Assortment: Genes segregate independently
Fig. 9-11: RrYy w/ RrYy
MENDEL’S SUMMARY
• The factors that control heredity are individual units
know as genes. In organisms that reproduce sexually,
genes are inherited from each parent.
• In cases in which two or more forms of the gene for a
single trait exist, some forms of the gene may be
dominant and others may be recessive.
• The two forms of each gene are segregated during the
formation of reproductive cells.
• The genes for different traits may assort independently
of one another.